This invention relates to a device for a dishwasher comprising a tub in which liquid, preferably water, by means of a circulation pump and at least one rotating wash arm, is sprayed onto the dishes and then collected at the bottom of the tub for recirculation. At the end of such a washing cycle, the spent water is discharged by means of a drain pump, the tub bottom being provided with means for collecting food waste from the dishes.
It is known in the art to provide the tub bottom with at least one sieve covering a sump in which water is collected before it is recirculated through the wash arm in the tub, as noted above. After each wash cycle, the water is emptied from the sump by means of the drain pump. Normally, the sieve slopes so that food waste dislodged from the dishes is carried towards a basket-shaped portion of the sieve which can be removed and which is comparatively easily accessible for cleaning. The cleaning, however, has to be done manually, and sometimes under flowing water.
In order to reduce the need for manual cleaning, it has previously been suggested to disintegrate or grind up the waste by passing it through rotating cutting elements which are connected to the circulation pump in the circulation system of the dishwasher, or are connected to the drain pump. Large bone chips and other hard objects are trapped by a coarse sieve in front of the cutting elements.
When using these devices, there is still a risk, however, that hard objects will bypass the coarse sieve and jam the cutting elements, and hence also jam the associated pump, because the cutting elements are usually integrated with the pump impeller or its drive. To remove such an object is both troublesome and time-consuming because substantial disassembly of the machine is required to gain access to the cutting elements.
It is also known in the art to clean the collecting part of the sieve by directing a stream of water onto it from one of the wash arms, thereby disintegrating the material, which is then discharged together with the water. However, this method has several drawbacks. It can only be used on fragile or easily divisible material wherein water action alone can cause sufficient disintegration. The water action is generally limited to a very small annular surface which constitutes only a small fraction of the total surface of the basket-shaped collecting container. Another disadvantage is that the arrangement consumes an excessive amount of energy by recirculating a much larger quantity of water than is required for cleaning the dishes. A further drawback is that the arrangement demands that the liquid level in the sump be maintained at an exact level which is above the inlet opening of the circulation pump but below the filter surface. Consequently, if the spray nozzles of the wash arm become clogged, there is a risk that the water level in the sump will rise sufficiently to cause the water jet coming from the wash arm to impact against the water surface instead of the food waste.